Combining the silver nanowire bridging effect with chemical doping for highly improved conductivity of CVD-grown graphene films

Abstract

Here, the conductivity of graphene films was significantly enhanced, with only a negligible loss in optical transmittance, by controlling the intrinsic electrical properties and domains through a combination of chemical doping and the deposition of a few one-dimensional (1D) silver nanowires (AgNWs). Ultraviolet photoelectron spectrophotometry (UPS) results and Raman spectra showed that the transparent conducting performance of the CVD-grown graphene film can be attributed to the chemical doping effect and the electric pathways provided by the AgNW bridging between graphene domains. Importantly, it was found that the transparent conducting performance of the AgNW modified CVD graphene films was significantly influenced by the types and sequence of chemical doping. Various combinations were investigated, including: (i) Au pre-treatment and then AgNW deposition, (ii) AgNW deposition and then Au post-treatment, (iii) acid (HNO₃) pre-treatment and then AgNW deposition, and (iv) AgNW deposition and then acid (HNO₃) post-treatment. Electrical conductivity and transmittance results showed that the combination of Au pre-treatment and subsequent AgNW deposition onto the graphene films is the most effective way to enhance the conductivity of graphene films for a variety of optoelectronic device applications, demonstrating a large reduction in the sheet resistance of the graphene film (ΔR_s ≈ 80%) without significant loss of transmittance. This is due to independent evolution of the chemical doping effect of Au and the bridging effect of the AgNWs on the poly-domain graphene. For deposition of AgNWs and subsequent Au post-doping, on the other hand, transmittance was reduced by more than 5% after Au post-treatment of the graphene films on which AgNWs had already been deposited.